Re: [Gumstix-users] kernel Hz

[Dave H. <dhy...@gm...>]

Hi Eduardo,

> I just have installed the sample char-driver module
> (excellent tool!) of Dave Hylands. It works fine, but
> i need to read from gpio faster than 100 Hz, wich is
> the default for jiffies count.

HZ is just what I happened to use as a timestamp for the events, If
you leave the debounce logic in, then it affects that. If your
external "switches" are already debounced, then you could use the much
higher resolution timer 0 (I don't recall the register name off hand),
but it runs at 3.6 MHz or something similar.

> How can i change this value?
> Do i need to change this on
> gumstix-buildroot/build_arm_nofpu/linux-2.6.15gum/include/asm-arm/param.h
> and recompile kernel?

Changing HZ can have severe performance impacts on your kernel. I
really don't recommend changing it. If you change it changes the rate
at which the kernel timer tick goes off.

> Where can i find some info about this?

Google for kernel HZ or linux HZ or other combinations.

--
Dave Hylands
Vancouver, BC, Canada
http://www.DaveHylands.com/